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In rabbits, an allelic series helps to determine coat color: \(C(\text { full color }), c^{\text {ch }}\) (chinchilla, gray color), \(c^{\text {h }}\) (Himalayan, white with black extremities), and \(c\) (albino, all-white). The Callele is dominant over all others, \(c^{\text {h }}\) is dominant over \(c^{\mathrm{h}}\) and \(c, c^{\mathrm{h}}\) is dominant over \(c,\) and \(c\) is recessive to all the other alleles. This dominance hierarchy can be summarized as \(C>c^{\text {ch }}>c^{\text {h }}>c\). The rabbits in the following list are crossed and produce the progeny shown. Give the genotypes of the parents for each cross: Phenotypes of parents a. full color \(\times\) albino b. Himalayan \(\times\) albino c. full color \(\times\) albino d. full color \(\times\) Himalayan e. full color \(\times\) full color Phenotypes of offspring \(1 / 2\) full color, \(1 / 2\) albino \(1 / 2\) Himalayan, \(1 / 2\) albino \(1 / 2\) full color, \(1 / 2\) chinchilla \(1 / 2\) full color, \(1 / 4\) Himalayan, \(1 / 4\) albino \(3 / 4\) full color, \(1 /_{4}\) albino

Step by step solution

01

Understand Dominance Hierarchy

Identify the dominance order of the rabbit allele series as noted: \( C > c^{ch} > c^{h} > c \). This tells us which alleles will dominate over others when paired together, impacting the resulting phenotype.

02

Analyze Cross (a) Full color \(\times\) Albino

Given progeny of 1/2 full color and 1/2 albino, the full-color parent must carry the recessive albino allele \( c \) to produce albino offspring. Therefore, the genotypes of the parents are \( Cc \times cc \).

03

Analyze Cross (b) Himalayan \(\times\) Albino

The offspring's phenotype ratio of 1/2 Himalayan and 1/2 albino suggests the Himalayan parent carries a recessive albino allele. Hence, the genotypes are \( c^{h}c \times cc \).

04

Analyze Cross (c) Full color \(\times\) Albino

With progeny of 1/2 full color and 1/2 chinchilla, the full-color parent must carry the chinchilla allele, making the genotypes \( Cc^{ch} \times cc \).

05

Analyze Cross (d) Full color \(\times\) Himalayan

With offspring of 1/2 full color, 1/4 Himalayan, and 1/4 albino, the full-color parent can have the genotype \( Cc^{h} \) to allow for Himalayan offspring, and the Himalayan parent \( c^{h}c \) to allow albino offspring, resulting in genotypes \( Cc^{h} \times c^{h}c \).

06

Analyze Cross (e) Full color \(\times\) Full color

The offspring's ratio of 3/4 full color and 1/4 albino implies that both parents are heterozygous for the albino allele, with genotypes \( Cc \times Cc \).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Genetics

Genetics is the study of how traits are passed from parents to offspring through genes. In this context, rabbits are used as a model to understand various genetic principles like inheritance and allele variations.
Genes are located on chromosomes and consist of DNA that dictates specific traits, such as coat color in rabbits. Different versions of a gene are known as alleles. In the case mentioned, the allelic series consists of the full color (C), chinchilla (c^{ch}), Himalayan (c^{h}), and albino (c) alleles. These alleles interact to produce the rabbit's coat color based on which are present in the genotype.
Key genetic principles include:

• Allele: Different forms of the same gene.
• Dominance: The relationship between alleles where one masks the effect of another.
• Inheritance: The process through which alleles are transmitted from parents to offspring.

Understanding these principles helps predict offspring traits based on parental genetics.

Dominance Hierarchy

In genetic interactions, dominance hierarchy describes the order of dominance among different alleles. It determines which allele will express itself over others in the phenotype.
The rabbit coat color dominance hierarchy is crucial for predicting the appearance of offspring. It is summarized as C > c^{ch} > c^{h} > c. This means:

• C is the most dominant and will always determine the full color phenotype when present.
• Next, c^{ch} leads to a chinchilla coat, unless C is present.
• c^{h} produces a Himalayan pattern but is masked by both C and c^{ch}.
• The c allele results in an albino phenotype only when paired with another c, as it is recessive to all other alleles.

This hierarchy helps in understanding which traits will be visible based on the rabbit's genotype.

Genotype

A genotype is the genetic makeup of an organism, specifically the alleles it carries for a particular trait. In our exercise, the genotype of rabbits includes two alleles for coat color, one inherited from each parent.
Identifying the genotype involves understanding which alleles are present and how they interact based on the dominance hierarchy.
For example, in the cross between a full-color rabbit (Cc) and an albino rabbit (cc), the offspring display a variety of genotypes like Cc, leading to both full-color and albino phenotypes. In this scenario:

• A Cc genotype results in full color due to the dominance of C.
• A cc genotype results in albino, as both alleles are recessive.

Thus, knowing the genotypes allows for accurate prediction of possible phenotypic outcomes in the offspring.

Phenotype

Phenotype refers to the observable traits or characteristics of an organism. In genetics, the phenotype is determined by the genotype and the interaction of alleles within the dominance hierarchy.
In the case of rabbit coat colors, the phenotypes include full color, chinchilla, Himalayan, and albino. These visible traits result from specific allele combinations in the genotype.
For instance, if we have the genotype Cc^{ch}, the phenotype would be full color because the C allele is dominant over all other alleles. However, if the genotype is cc, the phenotype will be albino, as no dominant alleles are present.
Understanding phenotypes helps in predicting what an organism will look like based on its genetic composition, providing insights into trait inheritance and variability.